The present invention relates to a fluid discharge device for discharging and feeding in a specified amount a variety of liquids such as conductive paste, adhesive, solder cream, grease, paint, hot melt, chemicals, and foods, or for uniformly coating a fluorescent material or the like onto the display surface of CRT, PDP, or the like with high accuracy, in production processes in the fields of electronic components, household electric appliances, and so on.
The fluid discharge device (dispenser) has conventionally been used in a variety of fields. In response to recent years"" needs for smaller size and higher recording density of electronic components, there has arisen a demand for a technique that allows an infinitesimal quantity of fluid material to be fed stably with high accuracy.
Otherwise, there is also a great demand for a fluid discharge method for uniformly coating a fluorescent substance on the display surface of CRT, PDP, or the like.
Taking the field of surface mount technology (SMT) as an example, the issues of the dispenser are summarized as follows in line with the trend towards higher mounting speed, miniaturization, higher density, higher quality, and automatization:
(1) Higher accuracy of coating quantity;
(2) Reduction in discharge time
(3) Smaller coating quantity per dot
Conventionally, a dispenser of an air pulse system as shown in FIG. 17 is widely used as a fluid discharge device. The technique is introduced in, for example, xe2x80x9cAUTOMATED ENGINEERING, ""93, Vol. 25, No. 7.xe2x80x9d
The dispenser of this system applies in pulses a specified amount of air supplied from a constant pressure source to the inside of a container (cylinder) 150 to discharge a specified amount of liquid corresponding to a rise in pressure inside the cylinder 150 from a nozzle 151.
For the purpose of feeding a fluid at an infinitesimal flow rate, a micro pump utilizing a piezoelectric element has been developed. For example, xe2x80x9cSUPERSONIC TECHNO, June Issue, ""59xe2x80x9d introduces the contents as follows. FIG. 18 shows a principle diagram, while FIG. 19 shows its concrete structure. When a voltage is applied to a laminate piezoelectric actuator 200, a mechanical extension occurs, and this extension is increased by the action of a displacement magnifying mechanism 201. Further, a diaphragm 203 is pushed upward in the figure via a thrust rod 202, and the capacity of a pump chamber 204 is reduced. In this stage, a check valve 206 of an inlet 205 is closed, and a check valve 208 of an outlet 207 is opened, discharging the fluid located inside the pump chamber 204. Next, when the application voltage is decreased, the mechanical extension decreases with decreasing voltage. The diaphragm 203 is pulled back downward by a coil spring 209 (restoring action), by which the internal capacity of the pump chamber 204 is increased to provide a negative pressure in the pump chamber 204. Due to this negative pressure, the inlet check valve 206 is opened to fill the pump chamber 204 with the fluid. In this stage, the outlet check valve 208 is closed. The coil spring 209 plays the important role of applying a mechanical pre-load to the laminate piezoelectric actuator 200 via the displacement magnifying mechanism 201 in addition to the action of pulling back the diaphragm 203. The above operations will subsequently be repeated.
This constitution employing the piezoelectric actuator could make it possible to realize a small-size, infinitesimal-flow-rate pump having excellent flow rate accuracy.
Out of the aforementioned prior art examples, the dispenser of the air pulse system has had the following issues.
(1) Variations in discharge rate due to discharge pressure pulsations
(2) Variations in discharge rate due to water head differences
(3) Changes in discharge rate due to liquid viscosity changes
The phenomenon of the issue (1) appears more noticeably as the cycle time becomes shorter and the discharge time is shorter. Accordingly, it has been practiced to take measures such as providing a stabilizer circuit for uniforming the air pulse height.
The issue (2) is ascribed to the reason that the capacity of an air gap portion 152 in the cylinder differs depending on a remaining liquid quantity H, and the degree of pressure change inside the air gap portion 152 is largely changed by the quantity H when a specified amount of high-pressure air is supplied. There has been an issue that the coating quantity decreases by, for example, about 50 to 60% as compared with the maximum value if the remaining liquid quantity is lowered. Accordingly, it has been practiced to take measures such as detecting the remaining liquid quantity H every occasion of discharge and adjusting the time duration of the pulse so that the discharge rate becomes uniform.
The issue (3) occurs, for example, when a material containing a large amount of solvent has changed in viscosity with a lapse of time. As a countermeasure against the issue, there has been taken a measure of preparatorily programming the tendency of the viscosity change on the time base in a computer and adjusting, for example, the pulse width so as to correct the influence of the viscosity change.
Any of the countermeasures against the issues has led to a complicated control system including the computer and has difficulties in coping with irregular changes in environment conditions (temperature and the like). Thus, the countermeasures have not been drastic proposals for solution.
Furthermore, when a piezo-pump employing the aforementioned laminate piezoelectric actuator shown in FIGS. 18 and 19 is used for high-speed intermittent coating of a high-viscosity fluid for use in the field of surface mount technology or the like, or when it is necessary to abruptly stop the outflow after a continuous coating, the following issues are predicted.
In the field of surface mount technology, recently, there has been a desire for, for example, a dispenser that instantaneously coats not more than 0.1 mg of an adhesive (viscosity: 100,000xe2x80x94several 1,000,000""s CPS) within a time of not longer than 0.1 second. Therefore, it is predicted that there is a need for generating a high fluid pressure in the pump chamber 204, and that the inlet valve 206 and the discharge valve 208 communicating with the pump chamber 204 are required to have a high response characteristic. However, in this pump accompanied by the passive discharge valve and inlet valve, it is extremely difficult to intermittently discharge a poor-fluidity, high-viscosity rheology fluid with high flow-rate accuracy at high speed.
For coating of an infinitesimal flow rate of high-viscosity fluid, thread-groove type dispensers, which are viscosity pumps, have already been developed into practical use. The thread-groove type dispensers allow preferable results to be obtained in continuous coating by virtue of their permitting a choice of pump characteristics that less depend on nozzle resistance, but are not good at intermittent coating in terms of the characters of the viscosity pumps. Accordingly, the thread-groove type dispensers have conventionally been provided in a constitution that:
(1) an electromagnetic clutch is provided between a motor and a main shaft of a pump, and this electromagnetic clutch is interlocked or opened at the time of discharge-ON or -OFF; or
(2) a DC servomotor is used for rapid rotation start or rapid stop.
However, in either case, since the response characteristic is determined by the time constant of the mechanical system, there have been restrictions on high-speed intermittent operation. Also, because of not a few indeterminate factors of rotation characteristics of the main shaft at transient responses (rotation starts and stops), there have been difficulties in strictly controlling the flow rate and limitations in coating accuracy.
In order to solve the aforementioned defects of the air pulse system, the piezo-system employing a laminate piezoelectric actuator, or the thread-groove type pump, the present inventor has already proposed a pump of infinitesimal flow rate in Unexamined Japanese Patent Publication No. 10-128217 (Japanese Patent Application No. 8-289543) described below.
This is to obtain an intake action and a discharge action of the pump by giving relative rectilinear and rotary motions between a piston and a cylinder by means of independent actuators, respectively, and electrically synchronously controlling the operations of the actuators.
In FIG. 20, reference numeral 301 denotes a first actuator constructed of a laminate type piezoelectric element. Reference numeral 302 denotes a piston that is driven by a first actuator 1 and corresponds to the direct-acting portion of the pump. Between this piston 302 and a lower housing 303 is formed, a pump chamber 304 whose capacity is changed by axial movement of the piston 302. In the lower housing 303 are formed an inlet hole 305 and outlet holes 306a, 306b communicating with the pump chamber 304.
Numeral 307 denotes a second actuator for giving relative rotary and swing motions between the piston 302 and the lower housing 303 and is constructed of a pulse motor, a DC servo motor, or the like. Numeral 308 denotes a motor rotor constituting the second actuator 307, while 309 denotes a stator.
A rotary member 310 is connected to the piston 302 via a disc-shaped plate spring 311. In order to transfer to the piston 302 the axial extension or contraction of the piezoelectric element that serves as the first actuator 301, the plate spring 311 has such a shape that it is easily elastically deformed in the axial direction. The rotation of the rotary member 310 is transferred to the piston 302 via the plate spring 311. With this construction, the piston 302 of the pump can simultaneously and independently perform rotary motion and rectilinear motion.
Numeral 312 denotes a coupling joint for supplying electric power from external to the first actuator 301 that performs rotary motion.
At a lower end portion of the lower housing 303, is mounted a discharge sleeve 314 having a discharge nozzle 313 at its tip. On the inner surface of this discharge sleeve 314 is formed a fluid passage 315 for making the outlet holes 306a, 306b and the discharge nozzle 313 communicating with each other. On the relative movement surfaces of the lower housing 303 and the piston 302 are formed fluid passage grooves 316b, 317b that allow the pump chamber 304 to communicate alternately with the inlet hole 305 and with the outlet holes 306a, 306b by the relative rotary motion of the lower housing 303 and the piston 302. These fluid passage grooves play the role of an inlet valve and a discharge valve of normal pumps.
Reference numeral 318 denotes a displacement sensor, while 319 denotes a rotary disc fixed to the piston 302. The axial position of the piston 302 is detected by the displacement sensor 318 and the rotary disc 319. In this proposal, a piezoelectric actuator is used for rectilinear motion and a motor is used for rotary motion.
For the intermittent dispenser according to the above proposal, a piezoelectric actuator is used for rectilinear motion and a motor is used for rotary motion.
In this case, it is required to give an electric power for electromechanical energy conversion via a conductive brush (coupling joint) to the electrodes of the piezoelectric element that is making a rotary motion. A high voltage of several hundred to several thousand volts is necessary for driving the piezoelectric element. Therefore, a large-diameter coupling joint has been needed, and this has led to the issue of an increased number of components and a complicated device. The conductive brush is accompanied by mechanical sliding, and this imposes a serious restriction on increasing the rotating speed.
In the patent specification of the aforementioned dispenser, in order to eliminate the conductive brush, there is proposed a method for arranging the piezoelectric element on the stationary side and rotating only the piston side to transfer an axial displacement of the piezoelectric element to the piston side via a pivot bearing.
However, in this case, a shift with aging of the axial position due to the wearing of the pivot section becomes a serious issue.
Moreover, in the field of circuit formation that has recently been going increasingly higher in accuracy and superfiner in size, or in the fields of electrode and rib formation for PDPs, CRTs, or other image tubes as well as manufacturing process for liquid crystals, optical disks, or the like, there have been such demands related to the fine-coating technique such as:
(1) both continuous and intermittent coating can be met, where, for example, continuous coating can be done and then rapidly stopped and, after a short time, continuous coating can be abruptly started. For this purpose, it is ideal to control the flow rate at an order of, for example, not more than 0.01 second;
(2) in either mode, high-accuracy coating can be implemented, where ultrahigh-speed coating can be implemented in the intermittent mode; and
(3) readiness for powder and granular material; for example, such trouble as powder-squeezing breakage and flow passage blockage due to mechanical shutoff of the flow passage is eliminated.
The present invention provides a fluid discharge device which greatly improves the prior art examples and device examples relevant to the infinitesimal flow-rate dispenser, and which meets new demands in the fine coating technique.
That is, by providing relative rectilinear and rotary motions between the piston and the cylinder and besides giving a fluid transport device by rotary motion, a relative gap between its stationary side and rotational side is changed by using the rectilinear motion, by which the fluid discharge rate is controlled.
The present invention enables the obtainment of a fluid discharge device that can discharge and coat, for example, an ultra-small quantity of high-viscosity fluid of poor fluidity with high accuracy at high speed, regardless of intermittent or continuous coating.
In accomplishing these and other aspects, according to a first aspect of the present invention, there is provided a fluid discharge device which comprises:
a shaft;
a housing in which the shaft is housed, the housing having an inlet port and a discharge port dedicated for a discharge fluid and serving for allowing a pump chamber defined by the shaft and the housing to be communicated with outside;
a device for relatively rotating the shaft and the housing;
an axial drive device for giving an axial relative displacement between the shaft and the housing to change a gap between the shaft and the housing; and
a device for pressure-feeding toward a discharge port side the fluid that has flowed into the pump chamber,
wherein the gap between the shaft and the housing is changeable by the axial drive device so as to allow a fluid resistance between the pump chamber and the discharge port to be increased or decreased.
According to a second aspect of the present invention, there is provided a fluid discharge device according to the first aspect, wherein the discharge fluid is conductive paste, adhesive, solder cream, or fluorescent material.
According to a third aspect of the present invention, there is provided a fluid discharge device according to the first aspect, wherein an opening of a discharge flow passage communicating with the discharge port is formed both in a discharge-port side end face of the shaft and in a relative movement surface which is a face opposite to the discharge-port side end face.
According to a fourth aspect of the present invention, there is provided a fluid discharge device according to the third aspect, wherein the gap between the shaft and the housing is a gap between the discharge-port side end face of the shaft and its opposing face which is changeable by the axial drive device.
According to a fifth aspect of the present invention, there is provided a fluid discharge device according to the fourth aspect, wherein a shallow groove for pressure-feeding the fluid radially is formed in the relative movement surface of the discharge-port side end face of the shaft.
According to a sixth aspect of the present invention, there is provided a fluid discharge device according to the first aspect, wherein the device for pressure-feeding the fluid toward the discharge-port side is a spiral-shaped groove formed both in an outer peripheral portion of the shaft and in a relative movement surface of an inner surface of the housing which is a face opposite to the outer peripheral portion.
According to a seventh aspect of the present invention, there is provided a fluid discharge device according to the first aspect, further comprising a displacement sensor which detects an axial relative displacement between the housing and the shaft, wherein with a signal of the sensor the axial relative displacement is adjusted by the axial drive device.
According to an eighth aspect of the present invention, there is provided a fluid discharge device according to the first aspect, wherein the axial drive device is moved or expanded and contracted by an electromagnetic contactless electric-power supplied by an electromagnetic contactless electric-power supply device.
According to a ninth aspect of the present invention, there is provided a fluid discharge device according to the first aspect, wherein the axial drive device is a Giant-magnetostrictive element.
According to a tenth aspect of the present invention, there is provided a fluid discharge device according to the first aspect, wherein inside an outer peripheral shaft which is a hollow shaft, is inserted a central shaft which makes relative movement in a direction opposite to the outer peripheral shaft, and a rate of change of size of a space defined by the outer peripheral shaft, a discharge-side end face of the central shaft, and a face opposite to the discharge-side end face is decreased during a move of the outer peripheral shaft.
According to an 11th aspect of the present invention, there is provided a fluid discharge device according to the tenth aspect, wherein the axial drive device is elastically supported at its both end portions, and the outer peripheral shaft and the central shaft are fitted to each of the end portions.
According to a 12th aspect of the present invention, there is provided a fluid discharge device according to the fourth aspect, wherein if a mean particle size of fine particles contained in the fluid is xcfx86d and a minimum value of the gap between the discharge-port side end face of the shaft and its opposing face is xcex4 min, then it follows that xcex4 min greater than xcfx86d.
According to a 13th aspect of the present invention, there is provided a fluid discharge device according to the first aspect, wherein the device for pressure-feeding the fluid toward the discharge-port side is a thrust-type groove formed both in an end face of the shaft and in a relative movement surface associated therewith.
According to a 14th aspect of the present invention, there is provided a fluid discharge device according to the first aspect, wherein a void portion is formed in a discharge-side end face of the shaft or in a housing in which the shaft is housed.
According to a 15th aspect of the present invention, there is provided a fluid discharge device according to the first aspect, wherein an area of an axial flow passage between the pump chamber and the discharge port is changed by a relative movement of the shaft and the housing performed by the axial drive device.
According to a 16th aspect of the present invention, there is provided a fluid discharge device according to the first aspect, wherein discharge flow rate is controlled by a combination of fluid resistance control performed by relative movement of the shaft and the housing with the axial drive device and rotational speed control of a motor.
According to a 17th aspect of the present invention, there is provided a fluid discharge method comprising:
controlling discharge flow rate by a combination of rotational speed control of a motor and fluid resistance control performed by relative movement of a shaft and a housing, for housing the shaft, to change a gap between the shaft and the housing so as to allow a fluid resistance between a pump chamber, defined by the shaft and the housing to be communicated with outside, and a discharge port of the housing to be increased or decreased.
According to an 18th aspect of the present invention, there is provided a fluid discharge device according to the eighth aspect, wherein with a rotation transfer shaft extending through a central portion of a cylindrical-shaped Giant-magnetostrictive element, or with a rotating sleeve in which an outer peripheral portion of a solid-shaped Giant-magnetostrictive element is housed, rotation is transferred to the shaft located within the pump chamber.
According to a 19th aspect of the present invention, there is provided a fluid discharge device which comprises:
a shaft;
a housing for housing the shaft, the housing having an inlet port and a discharge port dedicated for a pressurized fluid and serving for allowing a pump chamber defined by the shaft and the housing or by the shaft and the sleeve to be communicated with outside;
a device for rotating the shaft and the housing relative to each other;
a sleeve in which the shaft is housed or which has an opposing face opposing to the shaft at at least part thereof; and
an axial drive device placed between the housing and the sleeve or placed on either the housing or the sleeve and serving for giving an axial relative displacement between the shaft and the sleeve,
wherein a gap between the shaft and the sleeve is changeable by the axial drive device so that a fluid resistance between the pump chamber and the discharge port can be increased or decreased.
According to a 20th aspect of the present invention, there is provided a fluid discharge device according to the 19th aspect, further comprising a device for pressure-feeding toward a side of the discharge port the fluid that has flowed into the pump chamber.
According to a 21st aspect of the present invention, there is provided a fluid discharge device according to the 19th aspect, wherein an opening of a discharge flow passage communicating with the discharge port is formed both in a discharge-port side end face of the shaft and in a relative movement surface of its opposing face.
According to a 22nd aspect of the present invention, there is provided a fluid discharge device according to the 21st aspect, wherein a gap between the discharge-port side end face of the shaft and its opposing face is changeable by the axial drive device.
According to a 23rd aspect of the present invention, there is provided a fluid discharge device according to the 22nd aspect, wherein a shallow groove for pressure-feeding the fluid radially is formed in the relative movement surface of the discharge-port side end face of the shaft.
According to a 24th aspect of the present invention, there is provided a fluid discharge device according to the 20th aspect, wherein the device for pressure-feeding the fluid toward the discharge-port side is a spiral-shaped groove formed both in an outer peripheral portion of the shaft and in a relative movement surface of a sleeve inner surface, which is an opposing face opposing to the outer peripheral portion of the shaft.
According to a 25th aspect of the present invention, there is provided a fluid discharge device according to the first aspect, further comprising a displacement sensor which detects an axial relative displacement between the sleeve and the shaft, wherein with a signal of the displacement sensor, the axial relative displacement is adjusted by the axial drive device.
According to a 26th aspect of the present invention, there is provided a fluid discharge device according to the 19th aspect, wherein the axial drive device is an electromagnetostrictive element.
According to a 27th aspect of the present invention, there is provided a fluid discharge device according to the 26th aspect, wherein with one end of the electromagnetostrictive element provided as a fixed end and the other end thereof provided as a movable end, the fixed-end side is fixed to the housing while the movable-end side is fixed to the sleeve.
According to a 28th aspect of the present invention, there is provided a fluid discharge device according to the 22nd aspect, wherein if a mean particle size of fine particles contained in the fluid is xcfx86d and if a minimum value of the gap between the discharge-port side end face of the shaft and its opposing face is xcex4 min, then it follows that xcex4 min greater than xcfx86d.
According to a 29th aspect of the present invention, there is provided a fluid discharge device according to the 26th aspect, wherein high-frequency or ultrasonic vibrations are superimposed on drive of the electromagnetostrictive element.
According to a 30th aspect of the present invention, there is provided a fluid discharge device according to the 19th aspect, wherein a candle motor is used as the device for rotating the shaft and the housing relative to each other and the flow passage for conveyed fluid is defined between a rotor and a stator of the motor.
According to a 31st aspect of the present invention, there is provided a fluid discharge method comprising:
preparatorily programming coating quantities of discharge fluid necessary for individual coating-targeted sites; and
controlling a discharge flow rate of the discharge fluid by an axial relative displacement between a shaft and a sleeve for housing the shaft so that a gap between the shaft and the sleeve is changeable by the axial relative displacement so that a fluid resistance between a pump chamber, defined by the shaft and a housing or by the shaft and the sleeve to be communicated with outside, and a discharge port of the housing can be increased or decreased.
According to a 32nd aspect of the present invention, there is provided a fluid discharge device according to the 19th aspect, wherein the sleeve comprises a thrust plate having an opposing face opposing to the shaft, and a discharge nozzle.
According to a 33rd aspect of the present invention, there is provided a fluid discharge device according to the 32nd aspect, wherein the thrust plate is deformed by the axial drive device that gives an axial relative displacement.
According to a 34th aspect of the present invention, there is provided a fluid discharge device according to the 33rd aspect, wherein the axial drive device is an electromagnetic solenoid placed on the housing side.
According to a 35th aspect of the present invention, there is provided a fluid discharge device according to the 33rd aspect, wherein the axial drive device is a photoelectric element placed on the thrust plate.
According to a 36th aspect of the present invention, there is provided a fluid discharge device comprising:
a piston driven in a rectilinear direction by a first actuator;
a housing for housing therein the piston, the housing having an inlet hole and a discharge hole that are provided for a discharge fluid and formed in the housing, a pump chamber that is formed between the piston and the housing and communicates with the inlet hole and the discharge hole;
a cylinder arranged coaxially with the piston; and
a second actuator for giving a relative rotary motion between the piston and the cylinder,
wherein the relative rotary motion or rectilinear motion of the piston to the cylinder exerts a pumping action on the pump chamber, and the first actuator is moved or extended and contracted externally by an electromagnetic non-contact electric power discharge device.
According to a 37th aspect of the present invention, there is provided a fluid discharge device according to the 36th aspect, wherein the pump chamber is changed in capacity by a movement of the piston.
According to a 38th aspect of the present invention, there is provided a fluid discharge device according to the 36th aspect, wherein an operative portion of the first actuator is integrated with the piston.
According to a 39th aspect of the present invention, there is provided a fluid discharge device according to the 36th aspect, wherein electric power is discharged from outside to the first actuator in a non-contact manner.
According to a 40th aspect of the present invention, there is provided a fluid discharge device according to the 36th aspect, wherein the first actuator is a Giant-magnetostrictive element.
According to a 41st aspect of the present invention, there is provided a fluid discharge device according to the 36th aspect, wherein a flow passage groove for giving a pump intake action or a pump discharge action is formed on relative movement surfaces of the housing and the piston or the cylinder.
According to a 42nd aspect of the present invention, there is provided a fluid discharge device according to the 36th aspect, wherein the rectilinear motion of the first actuator is given in synchronization with the rotary motion of the second actuator by an electric signal.
According to a 43rd aspect of the present invention, there is provided a fluid discharge device according to the 36th aspect, wherein the rotation of the second actuator is a swing motion.
According to a 44th aspect of the present invention, there is provided a fluid discharge device according to the 36th aspect, wherein the second actuator is a scanning motor.
According to a 45th aspect of the present invention, there is provided a fluid discharge method comprising:
opening and closing an inlet port or a discharge port outlet of a flow passage by a relative rotary motion between a piston driven by an electromagnetostrictive actuator and a housing that houses therein the piston; and
discharging a discharge fluid by expanding and contracting the electromagnetostrictive actuator externally by supplying electromagnetic non-contact electric power.
According to a 46th aspect of the present invention, there is provided a fluid discharge method according to the 45th aspect, wherein the electromagnetostrictive actuator is comprised of a Giant-magnetostrictive element.